Most modern aircraft use integral fuel tanks. Thus, complicated and irregular structural joints must be sealed to prevent fuel leakage. In the past, sealing was accomplished by hand spraying or by use of grease gun type applicators. These application methods apply sealants in amounts far and above that required for actually accomplishing the seal. Another approach is to use preformed seals in grooves, for example, in spar cap to wing skin joints. However, such preformed seals are expensive and field repair is difficult to accomplish. Another approach is to fill a sealant groove with sealant after assembly via close out ports. Such an approach has several advantages: (1) sealant is applied in exactly the right place, (2) the amount of sealant required is kept to an absolute minimum, and (3) only a small number of ports are necessary, many of which can be externally located. An additional advantage is that upon resealing, the tanks need not be completely drained and cleaned.
However, the use of such close out ports require some method of sealing of the port after the grooves are filled. One approach is to use a flush head internally threaded bushing pressed into a port. A sealant applicator is threaded into the bushing and is used to inject the sealant under pressure on the order of 10,000 PSI. After filling of the groove a threaded plug is inserted into the bushing. However, such bushings depending upon a press fit and can work loose. Because the bushings are not designed to completely line the port they can cause severe problems when used in composite structures. A composite material is typically formed of layers of filamentary material in a resin matrix and the drilling of the port in the structure necessarily exposes these layers of filamentary material. Upon injection of the sealant under high pressure, delamination of the layers may occur, severely weakening the structure in the immediate area of the port.
Thus, it is a primary object of the subject invention to provide a close out fitting that is mechanically locked in place.
It is another object of the subject invention to provide a close out fitting that completely lines the port wall to prevent sealant from reaching the adjacent structure.
Another object of the subject invention is to provide a close out fitting that is flush to both surfaces.